Cars Emerge as Key Atmospheric Warming Force: Study

Feb 19, 2010 by Adam Voiland

Motor vehicles give off only minimal amounts of sulfates and nitrates, both pollutants that cool climate, though they produce significant amounts of pollutants that warm climate such as carbon dioxide, black carbon, and ozone. Credit: NASA's Langley Research Center

(PhysOrg.com) -- For decades, climatologists have studied the gases and particles that have potential to alter Earth's climate. They have discovered and described certain airborne chemicals that can trap incoming sunlight and warm the climate, while others cool the planet by blocking the Sun's rays.

Now a new study led by Nadine Unger of NASA's Goddard Institute for Space Studies (GISS) in New York City offers a more intuitive way to understand what's changing the Earth's climate. Rather than analyzing impacts by chemical species, scientists have analyzed the climate impacts by different economic sectors.

Each part of the economy, such as ground transportation or agriculture, emits a unique portfolio of gases and aerosols that affect the climate in different ways and on different timescales.

"We wanted to provide the information in a way that would be more helpful for policy makers," Unger said. "This approach will make it easier to identify sectors for which emission reductions will be most beneficial for climate and those which may produce unintended consequences."

In a paper published online on Feb. 3 by the Proceedings of the National Academy of Sciences, Unger and colleagues described how they used a climate model to estimate the impact of 13 sectors of the economy from 2000 to 2100. They based their calculations on real-world inventories of emissions collected by scientists around the world, and they assumed that those emissions would stay relatively constant in the future.

The on-road transportation sector releases significant amounts of carbon dioxide, black carbon, and ozone—all substances that cause warming. In contrast, the industrial sector releases many of the same gases, but it also tends to emit sulfates and other aerosols that cause cooling by reflecting light and altering clouds. Credit: NASA GISS/Unger

Snapshots of the Future

In their analysis, motor vehicles emerged as the greatest contributor to atmospheric warming now and in the near term. Cars, buses, and trucks release pollutants and greenhouse gases that promote warming, while emitting few aerosols that counteract it.

The researchers found that the burning of household biofuels -- primarily wood and animal dung for home heating and cooking -- contribute the second most warming. And raising livestock, particularly methane-producing cattle, contribute the third most.

On the other end of the spectrum, the industrial sector releases such a high proportion of sulfates and other cooling aerosols that it actually contributes a significant amount of cooling to the system. And biomass burning -- which occurs mainly as a result of tropical forest fires, deforestation, savannah and shrub fires -- emits large amounts of organic carbon particles that block solar radiation.

The new analysis offers policy makers and the public a far more detailed and comprehensive understanding of how to mitigate climate change most effectively, Unger and colleagues assert. "Targeting on-road transportation is a win-win-win," she said. "It's good for the climate in the short term and long term, and it's good for our health."

Due to the health problems caused by aerosols, many developed countries have been reducing aerosol emissions by industry. But such efforts are also eliminating some of the cooling effect of such pollution, eliminating a form of inadvertent geoengineering that has likely counteracted global warming in recent decades.

"Warming should accelerate as we continue to remove the aerosols," said Unger. "We have no choice but to remove the aerosol particulate pollution to protect human and ecosystem health. That means we'll need to work even harder to reduce greenhouse gases and warming pollutants."

By the year 2100, Unger's projections suggest that the impact of the various sectors will change significantly. By 2050, electric power generation overtakes road transportation as the biggest promoter of warming. The industrial sector likewise jumps from the smallest contribution in 2020 to the third largest by 2100.

"The differences are because the impacts of greenhouse gases accumulate and intensify over time, and because they persist in the atmosphere for such long periods," said Unger. "In contrast, aerosols rain out after a few days and can only have a short-term impact."

Unger's model finds that in 2020 (left), transportation, household biofuels and animal husbandry will have the greatest warming impact on the climate, while the shipping, biomass burning, and industrial sectors will have a cooling impact. By 2100 (right), the model finds that the power and industrial sector will become strongly warming as carbon dioxide accumulates. Credit: NASA GISS/Unger

Factoring in Clouds

For each sector of the economy, Unger's team analyzed the effects of a wide range of chemical species, including carbon dioxide, nitrous oxide, methane, organic carbon, black carbon, nitrate, sulfate, and ozone.

The team also considered how emissions from each part of the economy can impact clouds, which have an indirect effect on climate, explained Surabi Menon, a coauthor of the paper and scientist at the Lawrence Berkeley National Laboratory in Berkeley, Calif.

Some aerosols, particularly sulfates and organic carbon, can make clouds brighter and cause them to last longer, producing a cooling effect. At the same time, one type of aerosol called black carbon, or soot, actually absorbs incoming solar radiation, heats the atmosphere, and drives the evaporation of low-level clouds. This process, called the semi-direct aerosol effect, has a warming impact.

The new analysis shows that emissions from the power, biomass burning, and industrial sectors of the economy promote aerosol-cloud interactions that exert a powerful cooling effect, while on-road transportation and household biofuels exacerbate cloud-related warming.

More research on the effects of aerosols is still needed, Unger cautions. "Although our estimates of the aerosol forcing are consistent with those listed by the International Panel on Climate Change, a significant amount of uncertainty remains."

Related Stories

Pinpointing pollutant sources is an important part of the ongoing battle to improve air quality and to understand its impact on climate. Scientists using NASA data recently tracked the path and distribution ...

Global warming may proceed faster and be more severe than previously predicted according to research about to be published in the scientific journal Nature. Reductions in airborne particle pollution, or aerosols, as air qu ...

(PhysOrg.com) -- Though greenhouse gases are invariably at the center of discussions about global climate change, new NASA research suggests that much of the atmospheric warming observed in the Arctic since ...

Recommended for you

The ocean is a large reservoir of dissolved organic molecules, and many of these molecules are stable against microbial utilization for hundreds to thousands of years. They contain a similar amount of carbon ...

The fires superimposed on the satellite image of southeastern Australia designated by red spots may be indicative of "planned burns" by the Victoria region. This map: http://www.depi.vic.gov.au/fire-and-emergencies/planned-burns/planned-burns-now-and-next-10-days found on the Department of the Environment and Primary Industries for the State of Victoria shows the burns th ...

NASA's Aqua satellite captured an image of Typhoon Maysak as it strengthened into a super typhoon on March 31, reaching Category 5 hurricane status on the Saffir-Simpson Wind Scale. The TRMM and GPM satellites, ...

An international research team, led by a Virginia Tech geoscientist, has revealed information about how continents were generated on Earth more than 2.5 billion years ago—and how those processes have continued ...

The 2010 eruption of the Icelandic volcano Eyjafjallajökull grounded thousands of air flights and spread ash over much of western Europe, yet it was puny compared to the eruption 200 years ago of Tambora, ...

To understand when and why volcanoes erupt, scientists study the rocks left behind by eruptions past. A method called geobarometry uses the composition of volcanic rocks to estimate the pressure and depth ...

They've only considered short-term impacts on climate. Since CO2 has such a long atmospheric lifetime compared to aerosols, the aerosols shouldn't be considered when considering long-term impact. A proper list would rate industry higher and cows lower.

Do you have any idea how widely models are used by scientists of every type? I am sure that your not going off on astronomers, physicists, chemists etc. that use models to predict behavior in all sorts of systems. So why are you biased against the models used by climate scientists?

barakn "They've only considered short-term impacts on climate. Since CO2 has such a long atmospheric lifetime compared to aerosols, the aerosols shouldn't be considered when considering long-term impact. A proper list would rate industry higher and cows lower." What emits the most methane and can we control that source? CO2 is .04% of the atmosphere and Plant Scientists have found that almost all plants respond with faster and larger growth rates. Now where does all that extra CO2 go? Seems like the seas do more than the "Models" show.

More research on the effects of aerosols is still needed, Unger cautions. "Although our estimates of the aerosol forcing are consistent with those listed by the International Panel on Climate Change, a significant amount of uncertainty remains."

I don't like the sound of "aerosols." This suggests chemtrail experiments which noone wants nor needs.

Are we ignoring the NASA data that all the planets in the system are warming up? I agree with skeptic above: Drop the damn AGW banner and get human civilization on sustainable, non-polluting, advanced energy systems.

There are independent researchers who did slight modifications for fuel and air flow within internal combustion engines to increase efficiency over 75%.

Does the hard headed car manufacturing industry really have an amazing death grip on humanity? Only when we let them.

Another very useful tool to aid in formulating intelligent policy. Anything that can be done to help conceptualise the impact of these particulates/pollutants/greenhouse gases is a step in the right direction.

Jayk,"Hmmm, I had no idea that the oceans reached up into the atmosphere. Interesting, aufever." What I find is that the concept of CO2 being absorbed by Algar and Plankon is the source of our present oil deposits. By the way CO2 is acidic and easily absorbed by the oceans.

"Since CO2 has such a long atmospheric lifetime compared to aerosols, the aerosols shouldn't be considered when considering long-term impact"

Agreed.

"My bias against mickey mouse computer models is based on the fact that science is done from observations first, then checked."

Scientifically discovery always has involved modeling. Just read up on the history of the atom and how atomic models incrementally improved to the point that we knew what atoms looked like and behaved well before we could ever see them. Even incomplete and partially accurate models vastly improved our understanding and allowed us to make predictions. The current climate models are based on observation of climate and many other physical phenomena affected by climate, and have been highly successful at predicting future climate, so I don't see what you are getting at.

Did I get this right, or is this article subtly promoting geoengineering?

Cars, buses, and trucks release pollutants and greenhouse gases that promote warming, while emitting few aerosols that counteract it.

So how long before a self-appointed messiah figures it out and starts putting all sorts of extra pollutants in fuels to make cars emit cooling aerosols? This could easily bypass national/global policy, too. Everyone's free to put anything they want in their cars.

Well, this is great. Economists and climatologists joining forces to save the planet...

"though [cars] produce significant amounts of pollutants that warm climate such as carbon dioxide, black carbon, and ozone." Ozone? Oh no! We need to start a campaign against the evil lightening that constantly shows itself every few seconds around the planet. It's impact is several orders of magnitude greater than a car. I beg you, my fellow luddites, to rise up against nature.

They've only considered short-term impacts on climate. Since CO2 has such a long atmospheric lifetime compared to aerosols, the aerosols shouldn't be considered when considering long-term impact. A proper list would rate industry higher and cows lower.

And yet, it is the aerosols--combined with black carbon soot--which account for 90% of the melting of glaciers. 'Short-term impact' indeed! :)

We should be worrying more about black soot and aerosols than about CO2 at this stage of history. If the information in the studies holds true in light of other studies.

Worse, there is information to suggest that black soot may be responsible for a much higher percentage (up to four times according to one suggestion) than now attributed to it in the initial studies. Right now, black soot has been given a 30% responsibility out of that 90% overall responsibility for melting Himalayan glaciers. That number may well go up if the data leads that direction.

By the way, I also did not try to push anything with black soot as "the sole reason" for anything. Nonetheless, the 90% for aerosols combined with black soot does apply to the Himalayan glaciers. And, I have read a recent study that seems to apply it to the Arctic as well. When it is online, I will be glad to make you aware of it.

Aside from this, just keep on misreading. I have seen little set to break your misread-streak thus far. :)

put em in a box and given em calculators adn people cant figure out if the results of their figures is real or not. that they confuse reality with mathematics is at least well known and adapted for in physics, in other sciences such knowlege seems to be completely absent

by what right do the few have the power to experiment on the many by controlling the facts and forces aroudn their lives by the will and power of a gun weilded by the state?

what is the difference between joseph mengele who changed the circumstances of the lives of people by expermenting on them, and the social engineers whose methods are little more than experimentaion on people unfortunate to be the target of their completely fallacious premise that they have a right to control people and create outcomes based on some form of false aesthetic.

want to talk about assuming harm? they do this to people without even being liable for what happens. free from responsiblity, they sit in offices and experiment on people like mengele, but by usig 'social policy'.

may i ask where in the constiution does the rights of men are abrogated for controlled social outcomes by force of changing policy?

may i ask where in the constiution does the rights of men are abrogated for controlled social outcomes by force of changing policy?

In the preamble.

"We the People of the United States, in Order to form a more perfect Union, establish Justice, insure domestic Tranquility, provide for the common defence, promote the general Welfare, and secure the Blessings of Liberty to ourselves and our Posterity..."

"Promote the general welfare" is all the open interpretationists need to pass social reforms.

may i ask where in the constiution does the rights of men are abrogated for controlled social outcomes by force of changing policy?

In the preamble.

"We the People of the United States, in Order to form a more perfect Union, establish Justice, insure domestic Tranquility, provide for the common defence, promote the general Welfare, and secure the Blessings of Liberty to ourselves and our Posterity..."

"Promote the general welfare" is all the open interpretationists need to pass social reforms.

'Gay' used to mean 'happy' and 'liberals' used to respect individual rights and property.

"Promote the general welfare" is all the open interpretationists need to pass social reforms.

It is not in the interests of the general welfare that populations be used as guinea pigs. If social science is ever perfected to the extent that actual positive good can be done for the general welfare, then it will be time to implement some policies, not before.

Koen

In the case of the recent CO2 data it would appear that there is ~5 years lag time between temperatures and CO2 rise. Don't hold me to this as of yet, though.

Can CO2 help raise temperatures? Yes. In a lab it is easy to make it do so. Just make sure that the bell jar is filled with CO2 at levels far in excess of 'normal' and apply liberal heating using an IR lamp.

But, with the earth, it is not all that clear or certain as to how much if any at all. That is why I remain for the present a skeptic. Let's try to get some certainty--well, as much as the science will allow, at any rate.

The science is not settled by any means and the jury still is out in spite of the past claims of the IPCC and the mainstream media.

The article headline is seriously flawed. The article claims that ON ROAD emissions are the big problem. The headline says CARS. Cars are part of the on-road category but their footprint has been declining and EPA expects this trend to continue (for all types of car emissions.) Trucks and Transit Buses are the real problem. They burn diesel, an inherently polluting fuel. EPA expects truck and bus emissions to continue growing, but at a slower rate.

Individual car footprints are reducing CO2 and other emissions, however the number of cars on the roads continues to increase. The article makes an assumption, and whether that assumption is incorrect is open to interpretation. As long as that assumption is made clear, then the conclusions are valid.

My understanding is that methane gets oxidized into CO2 in the atmosphere yet I do not see any CO2 effects of animal husbandry. Is the CO2 derived from methane included in the effects of animal husbandry and landfill?

Various climate scientists are using a local CO2 reading and algorithmically messaging it into a global indicator of global CO2 levels, irrespective of lag times in CO2 atmospheric diffusion and absorption in Antarctic ice.

Please sign in to add a comment.
Registration is free, and takes less than a minute.
Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.